Device for reproducing information on the screen of a cathode-ray tube



June 10, 1969 CARON ET AL 3,449,620

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DEVICE FOR REPRODUCING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE,

Filed April 19, 1966 Sheet & of 14 lomw NN Sheet 3 :0 m FJ q J. CARON ET L EPRODUCING INFORMATION ON THE ww 5 926V 8 m 8 m m .m w w Im Q05 33350 v m b 8 5 229.230 v E m Um m um O 2o=oo 0 O V2205 w 5.5 E3

June 10, 1969 DEVICE or: R SCREEN OF A CATHODE-RAY TUBE Filed April 19. 1.966

I PI /NI B EEa mzou 2 INVENTORS JEAN CARON FIRMIN BIGO AGENT 0 mm. 9M M 5 t w Q June 10, 1969 CARON ET AL DEVICE FOR REPRODUCING INFORMATION 0 SCREEN OF A CATHODE-RAY TUBE Filed April 19. 1966 1. lllAL IVY" FIG.6

INVENTORS JEAN CARON FIRMIN 8160 AGENT June 10, 1969 J, CARON ET AL DEVICE FOR REPRODUCING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE Filed April 19, 1966 Sheet FIG. 7

INVENTORB JEAN CA RON BY FIRM/N B160 AGENT June 10, 1969 J. CARON ET AL 3,449,620

DEVICE FOR REPRODUCING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE Filed April 19 was Sheet 7 of 14 Q a o m (5 6%,," C9 39$ 2) O 9 v LL '2: F F

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JEAN CARON FIRM/N BIGO Zwa AGENT FIGJOC Sheet 5 of 14 June 10, 1969 CARON ET AL DEVICE FOR REPRODUCING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE Filed April 19. 1966 INVENTORS JEAN CARON FIRMIN BIGO AGENT BY Z -W F. )8.

Pm I E 2 u .i (l\ 530m 2 FI b o M g! :o 3.5.320 O 0mm o 8 0 E5 .5 6 a 003:0 G Q00 00 000 Q 0 h o w 2m 32m cozuutou h =o=u23o June 10, 1969 J. CARON ET AL 3,449,620

DEVICE FOR REPRODUCING INFORMATION ON THE scrum OF A CATHODE-RAY TUBE Filed April 19. 1966 Sheet 9 of 14 /%$L'JL Dischorg l7 1 Stages Eire 0% o- -R 69 cR2 2 Amplifying R 1 4f Stage FIG. 14 V v t 0| 0' 9 1'8 2'7 3'6 43 15 ATS FIG. 15

- INVENTORS JEAN CARON BY FIRMIN BIGO June 10, 1969 J CARdN ET AL 3,449,620 DEVICE FOR REPRODUGING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE /O of 14 Sheet Filed April 19. 1966 INVENTORS JEAN CARON FIRMIN BIGO AGEN June 10, 1969 CARON ET AL DEVICE FOR REPRODUCING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE Filed April 19. 1966 Sheet of 14 mp OC 5 m 0 N Now ER W A 1 CW NM R an Y B AGENT June 10, 1969 CARQN ET AL 3,449,620

DEVICE FOR REPRODUCING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE Filed April l9. 1966 Sheet of 14 EDC AMP EDP Amp llfier I l u Correction KMfir 1 1 mp I ler FIG. 17 C89 Transistor Siege F|G.18B F|G.18A FIG.18C

Charge rCircuit 3 7 ES 2 B Power Amplifier O-F-O 1 FIG. 20 R0 Discharge Circuit INVENTORB JEAN CARON FIRMIN BIG 0 AGENT 0 M .6 MW 0 ,3 3/ t e e m June 10, 1969 J CARQN ET AL DEVICE FOR RIB-PRODUCING INFORMATION ON THE SCREEN OF A CATHODE RAY TUBE Filed Aprll 19 1.966

June 10, 1969 J CARON ET AL DEVICE FOR REPRODUGING INFORMATION ON THE SCREEN OF A CATHODE-RAY TUBE Flled April 19 1966 Sheet INVENTORS EAN R C4 ON BY FI MIN 8160 United States Patent Int. Cl. I-l01j 29/70 US. Cl. 31s 22 ABSTRACT OF THE DISCLOSURE An alpha numerical display system for displaying rows and columns of symbols, in which the symbols are scanned in sequence in each row, the rows are scanned in sequence, and each symbol is scanned in a series of vertical scans before the next symbol is scanned. Each symbol has a plurality of points that are intensified in a predetermined sequence to provide a desired illuminated symbol. The horizontal scan wave is the sum of three sawtooth waves: the first of which has an amplitude corresponding to the length of a row symbols and a trace time corresponding to the time required to scan a row of symbols, the second of which has an amplitude corresponding to the width of a symbol and the adjoining space and a trace time corresponding to the time required to scan a symbol, and the third of which has an amplitude corresponding to the distance between adjacent horizontal points of a symbol and a trace time corresponding to the time for scanning one vertical line of a symbol. The vertical scan wave is the sum of a sawtooth signal having an amplitude corresponding to the height of a symbol and having a trace time corresponding to the time required to vertically scan a symbol, and a stepwave signal having a step height corresponding to the interval between rows and a step width corresponding the time required to scan a row of symbols.

The invention relates to a device for reproducing information on the screen of a cathode-ray tube, said information consisting of symbols defined by a characteristic train of electric modulation signals supplied from apparatus beyond the device and modulating the electron beam in intensity so that given points of a matrix luminesce, said point being arranged on lines lying one above the other and said matrices being arranged in at least one row, the spot of the electron beam scanning consecutively one column after the other of each matrix by the combined effect of the horizontal and vertical deflection members.

It is known that for the transfer, processing or storing of information (a numerical data) it is common practice to convert the information into coded electric signals, which are subjected to various appropriate treatments, particularly in devices such as computers.

After the process the information available in the form of electric signals at the output of said devices is given as the result. For direct use said electric signals have to be converted in turn into symbols, characters (at-data) and digits (numerical data).

It has been proposed to render such information visible on the screen of a cathode-ray tube. For this purpose each symbol is characterized by a train of consecutive electric signals and on the screen each symbol is formed by the luminescence of given appropriate points of an array of points (or matrix), which luminescence is produced by the modulation of the electron beam by each of said signals. Inside the matrix the points are arranged in lines and columns, whereas the matrices themselves are arranged in rows one below the other.

17 Claims ice By synchronising said train of signals and by scanning with the aid of the electron beam sequences of symbols can be formed on the screen, when the spot scans consecutively all matrices of the screen in the correct order.

The present invention relates to a device of this kind, particularly to a device of displaying the information stored in a computer. This device is characterized in that the horizontal deflection member is controlled by a combination of sawtooth signals comprising at least one first signal having an amplitude corresponding to the length of one row of matrices and a tracing time corresponding to the period in which the spot has to scan all matrices of one row, a second signal having an amplitude corresponding to the number of intervals between the columns of adjacent points of the same matrix and to the interval between two consecutive matrices of the same row, and having a tracing time corresponding to the period in which the beam scans one matrix, and a third signal having an amplitude corresponding to the interval between two columns of points of one matrix and having a tracing time corresponding to the period in which a column of points is traversed. The retracing times of the second signal and of the third signal are equal to each other and correspond each to the periods in which the beam changes over in one matrix from one column of points to the other column, the front edges of these second and third signals being such that their sum is equal to but opposite the front edge of the first-mentioned signal. The vertical deflection member is controlled by at least one sawtooth signal having an amplitude corresponding to the scan of one column of points of one matrix and having a tracing time corresponding to the period in which the beam covers a column of points and a retracing time during which the beam passes from one column to the other and from one matrix to the other in the same row, said sawtooth signal having exactly the same repetition frequency and the same phase as the third sawtooth signal of the horizontal deflection.

When the electron beam has to scan various rows of matrices, the vertical deflection member is, in addition, controlled by a step signal, the height of each step equal to the interval between two rows of matrices and the width of each step being equal to the time required by the beam to cover all points of a row of matrices. In this case the retracing time of the first sawtooth signal is equal to the time required by the beam for changing over from the end of one row of matrices to the beginning of the next row of matrices.

The horizontal and vertical deflection members are preferably magnetically controlled and comprise each two sets of coils. The first sawtooth signal is fed to one of the sets of coils of the device for the horizontal deflection of the beam, while an appropriate combination of the second signal and the third signal is fed to the other set of coils. In the same manner each of the two vertical deflection signals is fed to a set of corresponding coils.

The analysis of the sawtooth deflection signals of the desired amplitude and repetition frequency provides signals producing deflections of high amplitudes at low or average repetition frequencies and signals producing deflections of small amplitude at high repetition frequencies.

Splitting up into the combinations of horizontal and vertical members with the associated coils permits of adapting the electrical properties of each combination, for example the deflection sensitivity and the associated inductance to the required frequency and amplitude.

The electrical current characterized by a low or average repetition frequency and a large amplitude is preferably to an assembly having a great deflection sensitivity and a comparatively high natural inductance. The electric currents characterized by a high repetition frequency and a low amplitude are supplied to an assembly having a low deflection sensitivity and a comparatively low natural inductance.

The sawtooth signals are preferably obtained by charging a capacitor by a constant current and by discharging it by means of a suitable circuit.

In order to obtain synchronism between various signals for deflecting the electron beam and the modulation signals of the beam, the various discharge circuits are controlled by time-base signals, the time-base circuit itself being controlled by the apparatus beyond the device, for example a computer supplying said modulation signals. One of the time-base circuits supplies directly the step signal for the vertical deflection.

Thus the electron beam scans the points of each symbol in each matrix one column after the other and one matrix after the other in each row and then one row of matrices after the other, the points corresponding to the modulation signals being caused to luminesce.

The invention will be described with reference to the accompanying drawing.

FIGS. 1A and 1B show embodiments of a matrix for displaying a symbol on the screen of a cathode-ray tube and the array of matrices for displaying a series of symbols.

FIGS. 2A, 2B, 2C and 2D show three sawtooth signals for the horizontal scan of the screen and the combination of said signals.

FIG. 2Aa shows on a diminished scale the curve of FIG. 2A.

FIGS. 3A and 3B show each one signal for the vertical scan of the screen.

FIG. 4 shows a block diagram of a device according to the invention.

FIG. 5 shows a block diagram of the time-base circuit controlling the sawtooth generators.

FIGS. 6, 6A, 7, 8 and 9 show the schematic diagram of a bistable flip-flop circuit, the symbol of a flip-flop circuit, and the schematic diagrams of an inverting circuit ET, of a zero-point correction member and of the digital analogue converter respectively forming part of the timebase circuit of FIG. 5.

FIGS. IDA-10D show diagrams indicating the waveform of the signals at different points of the time-base circuit of FIG. 5.

FIG. 11 is a block diagram of the control-circuit of the first set of coils for horizontal deflection.

FIG. 12 shows a diagram for given operations of the control-circuit of the first set of horizontal deflection coils, the block diagram of which is shown in FIG. 11.

FIG. 13 shows a schematic diagram similar to that of FIG. 11.

FIG. 14 is a block diagram of the control-circuit of the second set of horizontal deflection coils.

FIG. 15 is a time diagram of the voltage at the terminals of the buffer capacitor of the circuit of FIG. 14.

FIG. 16 is a schematic diagram of the control-circuit of the second set of horizontal deflection coils.

FIG. 17 is a block diagram of the control-circuit of the first set of vertical deflection coils.

FIGS. 18A, 18B and 18C show a correction member for the voltage applied to the first set of vertical deflection coils and the waveform of said voltage at the input and the output of the correction member.

FIG. 19 is a schematic diagram of the circuit of FIG. 17.

FIG. 20 is a block diagram of the control-circuit of the second vertical deflection coils.

FIG. 21 is a schematic diagram of the circuit of FIG. 20.

FIG. 22 shows an embodiment of an amplifier supplying the modulation signals to the cathode of the cathoderay tube.

For the sake of clarity a practical embodiment will be described; the data indicated have to be taken by Way of exam le,

I wimp" 4 FIGS. 1A and 1B show how symbols, for example characters or digits can be displayed on the screen of a cathode-ray tube, the electron beam intensity of which is varied by modulation signals.

FIG. 1A shows a matrix M of points to be scanned by the electron beam for displaying one of the symbols. In the embodiment shown said matrix comprises 35 points (5 columns and 7 lines), scanned :by the beam in the given order. The beam thus scans one column after the other, starting at the left-hand top. Each of the points is normally dark and it luminesces when a modulation signal is fed to the electron beam at the instant when the spot passes the point concerned.

In order to Write for example the character B (ee FIG. 1A) the modulation signals have to be fed to the electron beam when it strikes the points 1, 2, 3, 4, 5, 6, 7, 8, 11, 14, 15, 18, 21, 22, 25, 28, 30, 31, 33 and 34.

Such matrices are, of course, imaginary arrays; they appear only in the form of luminescing dots on the screen, when scanned by the electron beam.

It will be seen that a given number of identical matrices may be combined in p rows and n columns (see FIG. 1B) in order to write a series of symbols (for example a text), in which the number of the modulation signals and their distribution are different for two different symbols. In FIG. 1B each matrix M has the number of the row and that of the column.

The electron beam has to cover a composite path on the screen. It starts at point 1 of the first matrix M11 of the first row and follows the first column of this matrix to point 7, after which it passes to point 8, the first point of the second column, which is covered to point 14 and so on to point 35. The beam then passes to point 1 of the matrix M which is scanned in the said manner and this applies to all matrices of the first row up to point 35 of the matric M The beam then jumps to point 1 of the first matrix M21 of the second row, which is scanned in the manner described above; all rows of matrics are thus traversed to point 35 of the matrix Mpn, after which the beam returns to point 1 of the matrix M11.

According to the invention this scanning mode is obtained by means of the combination of the horizontal sawtooth deflections H H or H shown in the same scale in FIGS. 2A, 2B and 2C respectively and with the vertical deflections V and V shown in FIG. 3 on different scales.

FIG. 2A shows the first part of a sawtooth signal A, which is shown on a smaller scale in FIG. 2Aa; the tracing time t thereof is equal to the period of time required by the beam to scan the length h of a row of matrices M (see FIG. 1B) and the retracing time t is equal to the time required by the beam for passing over from the end of one row of matrices to the beginning of the next row. In order that the beam can scan the whole length of a row of matrices, the amplitude of the signal A is furthermore equal to h (see FIG. 2Aa).

If, as stated above, the matrices are each formed by 5 columns of 7 points and if each row comprises 40 matrices, the scanning time for one column of points in one matrix may be 7 ,usec and the transitional time between two consecutive columns and two consecutive matrices may be 2 sec. The scanning time of one matrix is thus 5 (7+2) =45 -sec, including the interval of time between the matrices. Under these conditions of scanning time of a row, that is to say the tracing time 1 of the sawtooth signal A is 45 40=l800 p.566. The time required by the 'beam to pass over from the end of one row of matrices to the beginning of the next row may thus have the value of 45 asec so that the retracing time t of each sawtooth signal A is 45 sec and the overall time in this particular case 1845 sec.

The deflection H can be obtained by means of a signal formed by a train of sawtooth pulses A, fed to a magnetic deflection member. The displacement of an electron is proportional to the strength of the associated magnetic field, which itself is proportional to the current supplied to the deflection member. The deflection H can thus be obtained by means of the sawtooth current signal A. This also applies to the other deflections of the beam.

The deflection H has superimposed on it the combination of two deflections H and H which are produced by the sawtooth signals B and C illustrated in FIGS. 2B and 2C. The retracing time t of the signal B is equal to the interval between two consecutive matrices, for example, to 2 sec. The tracing time r is the time necessary for scanning one matrix, for example, 452.=43 sec. The amplitude h of the signal B determines the interval between two consecutive matrices.

The deflection H is obtained by the signal C, having a retracing time t equal to the interval between one column of points and the next column of points in the same matrix; this time is indicated by t and has a duration of, for example, 2 ,usec. The tracing time t of the signal C has a duration equal to the scanning period of one column, for example, 7 ,usec. The amplitude h of the signal C partially determines the interval between two consecutive columns of the same matrix.

The superimposition of the three signals A, B and C results in the curve D of the horizontal deflection H shown in FIG. 2D. Since the values of k h r and t are chosen so that the sum of the rear edges of the signals B and C is equal to the front edge of the signal A, the deflection H is characterized by a sequence of steps having a duration of 7 sec, during which the beam is not displaced in the horizontal direction, after which the beam performs a jump of a duration of 2 usec. During these jumps the beam is deflected either in the same matrix (bc, de, yg, hi, from one column to the other, or from one matrix to the other (ja, During the period of 7 ,usec (steps ab, cd, ef, gh, ij, a'b', during which the beam is not deflected horizontally, the beam can scan a column in a vertical sense. The interval between two columns of one matrix is equal to h and the interval between two matrices is equal to h the point a, like the point a is located on the sawtooth signal A. The same scanning process restarts at a and goes on until the end of a row.

For the beam scan of each column this horizontal deflection H has superimposed on it a vertical deflection V (FIG. 3A), which is obtained by means of a sawtooth current signal E. The amplitude v thereof is equal to the height of one matrix M. Moreover, the tracing time t is equal to the scanning time of a column, for example 7 sec, that is to say the period of one step of the signal D. The retracing time t must be equal to the interval between the columns or between the matrices, for example 2 sec, that is to say the period of one jump of the signal D.

By the combination of the deflection H and V the beam is capable of scanning any point of all matrices of one row. For the transition of the last matrix of one row to the first matrix of the next row the beam is furthermore deflected vertically (V FIG. 3B). This deflection is obtained with the aid of a signal F, formed by a step current, each step of which has a duration 1 equal to the scanning period for one row of matrices, here for example 1800 used; the height of the steps may be equal to the interval between two consecutive rows of matrices. The end of one step is joined at the beginning of the next one by a rectilinear part of the signal R of a duration dp equal to the time required by the beam for passing from one row of matrices to the next one, for example 45 ,usec., which corresponds to the jump between two steps. The overall duration of one step 1 and a jump R of the signal F is therefore 1845 sec.

When the beam has scanned the last matrix M (FIG. 1B) it has to return to the matrix M11. The period of such a flyback exceeds the interval between two consecutive rows of matrices and it is assumed here to be 135 sec. Since twelve rows of matrices are provided, the signal P must have twelve steps and eleven jumps R The overall period of the signal F, inclusive of the retracing time of ,uSC., is therefore ,usec. In order to reset the beam from the end of the matrix M in the horizontal direction and in the vertical direction with the same speed for scanning the matrix M11, the retracing time t of the sawtooth signal A is also chosen to be 135 ,uS6C., which is therefore the duration of the rectilinear part of the signal F. The value of 135 sec. is chosen in connection with the fact that this is a multiple of 9 ,usec., which is the period of time of the signals C and E and a multiple of 45 ,usec., the period of the signal B, so that at the end of the retracing time of the signals A and F the signals B, C and E are at the beginning of their tracing times t t and r respectively.

FIG. 4 shows diagrammatically how the various signals of FIGS. 2 and 3 are obtained and combined to cause the beam to scan the screen E of a display tube T The tube T comprises four sets of coils of a type known in television technique for the deflection of the electron beam. Two of these sets H and H serve for the horizontal deflection and two further sets V and V serve for the vertical deflection.

The set H receives a signal from a sawtooth generator G and a form generator G this signal A is shown in 'FIG. 2A. The set H receives a combination of signals B and C, shown in FIGS. 2B and 2C, from sawtooth generators G and G and a form generator G The set V receives a signal E of FIG. 3A from a sawtooth generator G and a form generator G As will be explained more fully hereinafter, the form generators GAG, G and G are especially intended to form the sawtooth signals developed by generators G G and G as far as linearity and special forms during retrace time is concerned. It is also possible to insert desired corrections in the original sawtooth signals with the aid of these form generators.

The generators G G G and G are connected to the outputs S S S S and S respectively (see FIG. 4) of a time-base circuit B, for the control in synchronism. The output 8,, of the time-base circuit is connected through a form generator G to the set V in order to obtain the step signal F of FIG. 3B.

The time-base circuit B is controlled by signals, for example, from a computer having the information in its store. The computer supplies its signals to the inputs E E of the time-base circuit B These signals are reference or clock signals (HOR) and field synchronising signals (SYN) preceding the signal (HOR) with each field. In this embodiment the signal (HOR) is a square-Wave signal having a repetition frequency of 1 mc./s.; the square waves have a duration of 0.5 ,usec. and an interval also of 0.5 sec. (see FIG. 10A).

The computer also transmits modulation signals (MOD) via the input E to the electron gun C of the tube T through a video amplifier AV, the diagram of which is shown in FIG. 22.

The block diagram of the time-base circuit B is shown in FIG. 5. It comprises bistable flip-flops interconnected so that they form counters CB CB CB C13 and CB which divide by 3, 5, 9, 12 and 41 respectively. These numbers depend upon the values chosen in this embodiment. In another embodiment said numbers may be diflFerent.

It is known that a bistable flip-flop forms a divide-by-2 counter, which means that at the output the circuit provides a single pulse for every two pulses fed to its input; k stepwise connected bistable flip-flops thus form a divideby-2 counter. In order to form counters having a denominator unequal to the k power of 2 use has to be made of known feedbacks. For example, in order to form the divide-by-9 counter, the input of which receives the signal (HOR), three bistable flip-flops MVB MVB and MVB are connected stepwise (forming a counter dividing by 2 :8), whilst the output Q of MVB is connected to an input P of a fourth flip-flop MVB the output Q of which is connected to the input R of MVB whereas a further input? of MVB receives the signal (HOR). With such a feedback loop, comprising the flipflop MVB there is obtained one pulse at the output S of the inverting element I for nine pulses (or square waves) of the signal (HOR) applied to E The element I is connected to the output of and-gate P One input of gate P0 is connected to the inputs P and I of the flip-flop MVB and the other input and gate P0 is connected to the output Q of MVB The other inverting elements I in FIG. 5 are also provided according to need in the time-base circuit B With the aid of similar couplings other counters can be obtained; for example the counter CB. is obtained by means of a counter comprising six stepwise connected multivibrators which provide without the need for further means a dividing number of 2 :64. A divide-by-45 counter CB with the output S is obtained by the combination of divide-by-9 and divide-by-S counters.

FIG. 6 shows a practical flip-flop circuit MVB. The collector of the two n-p-n transistors T T 2 are connected to the positive terminal of the voltage source U through the resistors R and R and the emitters thereof are directly connected to ground, to which also the negative terminals of the sources U and U are connected. The potential at the base of the transistor T is statically determined by the resistor bridge formed by the resistors R and R in series connection and by the resistor R The free end of the resistor R is connected to the positive terminal of the voltage source U and the free end of the resistor R is connected to the negative terminal of the voltage source U The base of the transistor T is connected to point P the junction of the resistors R and R The potential at the base of the transistor T connected to the point P is statically determined in symmetry by the resistors R R and R The crossings of the circuits of the collectors and the bases have two semiconductor diodes D and D and capacitors C and C are connected in parallel with the two resistors R and R respectively. The cathodes of the semiconductor diodes D and D having a selective effect in the transmission of the control-pulses to the bases of the transistors T and T receive the positive bias voltage U via the two resistor bridges formed by R and R and by R and R respectively. This positive bias voltage forms a threshold for avoiding any premature operation of the circuit under the action of random low negative pulses having the nature of interference. The input circuits of the control-pulses comprises two capacitors C and C which are charged in the rest position by the positive voltage U via the resistors R and R respectively up to a voltage across capacitors C and C respectively which is the ditference between the voltage U and the voltage present at the junction of the voltage dividers R and R and R and R respectively. The normal control-pulses changing over the flip-flops consist of short-duration pulses bringing the inputs R and P for a short time at ground potential. To these inputs are furthermore connected the cathode of the semiconductor diodes D and D the anodes of which are connected to the points P and P respectively, corresponding electrically to the input electrodes of the capacitors C and C The diodes D and D forming a crossing between point P and the collector of the transistor T and between the point P and collector of the transistor T provide the charge of the capacitors C and C in accordance with the instantaneous state of the flip-flop circuit. At point R there is provided an additional input for the cathode of the diode D the anode of which is connected to the point P This additional input R, when it is at ground potential, neutralises the effect of the bistable multivibrator on the control-pulses applied to the input P. These inputs are employed to form dividing counters which cause the time-base circuit B; to operate in the desired manner. The input R ensures that the flip-flop maintains a given state.

The arrangement has furthermore an input Y, which is connected to the cathode of the diode D the anode of which is connected to point P of the base circuit of the transistor T This input Y serves for receiving the synchronising pulses transmitted for each new scanning period of the raster by a zero-correction device RAZ (see FIG. 5) which resets the flip-flops MVB in known manner to zero before the scan of the next raster restarts. Even in the case of disturbances during a raster scanning period it is thus ensured that the flip-flops are invariably in the zero-position at the beginning of a raster scan. The outputs Q and 'Q' of the arrangement are directly connected to the collectors of the transistors T and T respectively.

Practical values of the flip-flop arrangement of FIG. 6 are given in the following table:

FIG. 6A shows symbolically MVB of FIG. 6 in which the inputs and outputs are arranged like in the block diagram of FIG. 5. It is not necessary to use all inputs and outputs for each fiipflop MVB, since in certain cases some of the flipflops are not connected.

The and-gates P0 are shown in conjunction with the inverting element I in FIG. 7. They are formed by the parrallel-connected diodes D to D The inverting element I is formed by the transistor T the emitter of which is connected to ground. The and-gates followed by the inverting elements I) are identical and are each a normally available part, a variable number of inputs of which is used at the place where an element is employed. If a single input is used, the gating effect is meaningless and only the inverting element I is active, but the impedances and the signal levels have to be maintained correctly. In such a case the diagram of FIG. 5 shows only the block representing the inverting function. FIG. 7 shows the work point of the transistor T in the rest position (in which all cathodes of the diodes D to D are positive to point P said point being determined by the resistors R R and R the junction P of which, lying between R and R is connected to the base of the transistor T and by the values of the voltages U and U ground. The transistor T is fed by the voltage U via the resistor R The signals directly supplied by or through inverting stages by the bistable 'multivibrators MVB are applied to each of the input terminals P to P formed by the cathodes of the diodes D to D The capacitor C serves for rapid transmission of the pulses from the junction P of the anodes D to D to the base of the transistor T By way of example the values of the elements of a practical arrangement as shown in FIG. 7 are given below:

D15, D16, D17, D18=IN914 The zero-correction member RAZ is also a normally available part; only one is used in this case; it is shown in detail in FIG. 8. The construction of the input circuit is identical to that of the input circuit of an and-gate. The collector of the transistor T which receives the voltage U via a resistor R is connected to the base of the transistor T the emitter of which is directly connected to ground and the collector of which is fed via the 9 10 resistor R by the voltage U Only a single diode of the the correction stage EDC, which forms the input circuit circuit of FIG. 8 is used, and for substantially the whole of an amplifier, the block diagram of which is shown synchronising period the cathode of said single semiconin FIG. 17 (it shows the current source GFC of FIG. ductor diode, to which is fed the synchronising signal together with the vertical deflection coils V and V (SYN), is positive with respect to the anode thereof; that The values of elements used in a practical embodiment is to say +6 V. Thus transistor T draws current thereby as shown in FIG. 9 are given below. cutting off transistor T leaving the collector of transistor R25=40009 106220000 R27=R28=1000Q T at a fairly high and posltive voltage. D ur1ng the 0.5 R2924000Q R30=390Q T6=2N 1613 p.866. of the synchromsing pulse the 1nput srgnal becomes U29: V U30=|+24 v zero and the voltage of the collector of the transistor T 10 becomes even approximately Zero; th d i d t l- In the numerical example the various counters are relapulse is thus fed to the inputs Y of the bistable multitlvely connected so that the Output 1 Provides Pulses ibrato MVB, of a width of 2 sec. and intervals of 7 ,usec. (FIG. 10A), By way of example the values of the elements empolyed the Output 2 a Signal formed by Sequences of eleven in a practical embodiment of the arrangement shown in pulses of 45 and intervals of 1800 twee, followed y FIG 3 are given b l a twelfth pulse of 45 sec, having an interval of 1890 sec. from the preceding pulse and of 1710 usec. from the k9 R23 750n first pulse of a new sequence of eleven pulses (see pulse 2 8209 T sequence (,6) of FIG. 10C), the output 8;, pulses Y of 2 sec. and intervals of 43 #860. (see FIG. 10B), the out- T4, T5=2N 744 U20=+24v. U22=-10v. 1 U23=+10VI U24=+10V. put S pu ses (6) of 45 ,usec. and intervals of 1800 ,usec.

(FIG. 10C) and the output S pulses (e) of 90 ,usec. and FIG. 9 shows the digital to analogue converter U of intervals of 22,095 ,usec. (FIG. 10C). The function of FIG. 5. The transistor T is the active element, whose colthese signals will be explained hereinafter.

lector is is fed via the resistor R by the positive voltage 25 The generators G G G and G are based on the U and whose base is connected to a fixed positive volt- Same principle for producing sawtooth signals: they comage U prise each a buffer capacitor C charged by a constant The emitter of the transistor T is connected to point current and discharged via a circuit which becomes con- P29 and via resistor R to ground, to which is also conducting by the signals applied to the outputs S S S S nected the negative common terminal of the positive volt- 30 and S of the time-base circuit B ages U and U FIG. 11 shows the block diagram of the generators The four resistors R to R have the values 4 2 1p G G of FIG. 4 for the supply of a sawtooth signal like and 1p respectively and 4p is the value of the resistor R the signal A of FIG. 2Aa to the coils H H The four inputs P to P forming the free ends of the The capacitor C is charged through a charging cirresistors R to R the other ends of which are connected cuit E and discharged via two discharging stages E to point P are connected to the corresponding points of and E The individual strength of the discharge currents the divide-by-12 counter CB can be controlled by the variable resistors R and R The converter of FIG. 9 operates as follows: The two discharging circuits are absolutely necessary,

At the instant O (at the beginning of a signal F; see

since the fly-back time of the beam from the last row also the table of commutations hereinafter) the points P 40 of matrices to the first row is longer than the fly-back time to P are, in accordance with the corresponding points of from ne rOW to the next (135 nsec. instead of ,usec. the counter CB to which they are connected, at a posiin this case).

tive voltage approximately equal to U The current This difiiculty is solved in the following manner. In a through the base-emitter circuit is determined by the charnormal retracing time of 45 ,usec. the two discharging ciracteristics of the voltage divider formed by the resistor 45 Cuit E and p ate sim lt ne sly n Pa R and the assembly of resistors R to R which are Whilst the pulses of 45 ,usec. from the outputs S and S connected in parallel, and by the voltages at points P to of the time-base circuit B coincide. After twelve steps the P Consequently, at the instant O the potential differences two circuits E and E operate one after the other. The across said voltage divider is at a minimum, so that the circuit E receives first a pulse of 45 ,usec. from the outbase-emitter current is at a minimum and also the collecput S (see signal 8 in FIG. 10C), then with a delay of tor current I of the transistor T is at a minimum. 90 ,usec. (equal to the difference in retracing times 90- During the operation of the multivibrators MVB to 13545 ,usec.) the circuit E receives a pulse of 45 tsec. MVB of FIG. 5 the points of the inputs P to P have a from the output S of the time-base circuit B (see sigvoltage approximately equal to ground potential in the nal ,8 in FIG. 10C; of e time difference between the two given order corresponding to the table below. Owing to first pulses of the signals 13 and 6).

the chosen ratio between the resistors R to R each However, the charging time of the capacitor C should potential variation at points P to P increases the colremain constant irrespective of its discharging period. lector current of the transistor T by a value Al and The charging time determines the amplitude of the sawafter the twelfth step the current returns to the initial tooth and hence the amplitude of the beam deflection. value I Each potential variation at points P to P In order to ensure that during the longer retracing therefore forms one step of the signal F. time of 135 sec. the capacitor C does not receive fur- Order of commutations 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Points approximately at ground potential.

Increase in current I expressed Thus a step voltage appears between the point P and ther charge than during the normal retracting time of 45 ground which voltage decreases progressively during the ,nsec, a device DC interrupts the supply of charge for two eleven steps after the initial value, the initial value being thirds of the retracing time of 135 sec. (here used, regained at the twelfth commutation. The output S recorresponding to the difference between the discharging ceiving thus the signal (0) of FIG. 10D, is connected to 75 times of and 45 sec.), for example by cutting olf a charging transistor T of the circuit EC, see FIGS. 12 and 13, by means of the signal (E) at the terminal S Between the capacitor C and the sets of coils H and H there is connected a power Stage EP, having an impedance matching input circuit formed by the transistors T T and T connected like emitter followers (see FIG. 13, which shows an embodiment of the device of FIG. 11). The collectors of the power transistors T and T are fed from a direct voltage Source 5 through a choke B Owing to the low DC resistance of the choke in the collector circuits of the transistors T and T the linearity of the scan is disturbed. This can be corrected by applying a sawtooth component to the charging current of the capacitor C A correction signal generator G may be simple formed by a transistor T which forms part of the circuit described above and which supplies the required correction signal to the base of the charging transistor T Moreover, if the screen E of the cathode-ray tube T is flat, it is necessary to correct the resultant deviation from the linearity of the image by the so-called S-correction. For this purpose the charging current of the capacitor C is modulated so that the sawtooth signals A are slightly rounded off and slightly flattened at the beginning and at the end of the leading edges, the two flattened parts corresponding to the positions of the spot near the edges of the screen E The modulation voltage should have a parabolic shape; it is applied to the collector circuit of the transistor T, by the generator G formed by two transistors T and T which are connected stepwise.

From FIG. 13 it will be seen that for this purpose the base of the transistor T connected to point P is governed, in addition, by the interrupter DC through the variable resistor R and by the correction-voltage generator G via the resistor R which connects point P to the base of the transistor T The emitter of the transistor T receives a voltage U via a fixed resistor R and a variable resistor R having a common junction P to which is connected the parabolic correction-voltage generator G which is otherwise connected to the collector of the transistor T of the part G The resistor R thus forms part of the emitter circuit of transistor T and of the collector circuit of transistor T so that the coupling between said transistors is ensured.

The detailed diagram of FIG. 13 is an embodiment of the block diagram of FIG. 11. In the charging interrupter DC the emitter of the transistor T receives the voltage U and its base is connected to its emitter by the diode D the cathode of which is connected to said emitter. The collector of the transistor T is connected via the variable resistor R to the base of the transistor T The charging interrupting signal (6), the pulses of which have a duration of 90 ,usec. and which emanates from the output S of the time-base-circuit 3;, is applied to the cathode of the diode D the anode of which receives the voltage U through a resistor R From the anode output of this diode the signal is transmitted to the base of the transistor T via the capacitor C and the resistor R in series connection.

In the sawtooth correction signal generator G the emitter of the transistor T receives a voltage U and the base receives via the resistor R the signal of the collector of the transistor T The collector of the transistor T is connected to ground via the resistor bridge formed by the series-connected resistors R and R The junction P of these two resistors is partly decoupled to ground by the capacitor C and is coupled with the base of the transistors T via resistor R In the discharging stage E the collector of the transistor T is connected to point P the non-ground connected end of the capacitor C through the variable resistor R The emitter of this transistor is fed by the voltage U A diode D connected between the emitter and the base, prevents the latter from becoming negative relative to the emitter. The control-signal of the stage E from the output S of the time-base circuit B is applied to the cathode of a diode D the anode of which receives through the resistor R the voltage U The signal thus produced at point P is transmitted to the base of the transistor T through the series connection of the resistor R and the capacitor C The base of transistor T is connected by way of diode D to source U of supply voltage, and the emitter of transistor T is also connected to source U In the discharging stage E the collector of the transistor T (point P is connected via the resistor R t0 the base of the transistor T of the part G and to point P via the diode D and the variable resistor R The emitter of the transistor T receives the voltage U The base of the transistor T is connected to the emitter through the diode D which prevents said base from becoming negative to the emitter.

The control-signal of the stage E from the output S of the time-base circuit B is applied to the cathode of the diode D the anode of which receives the voltage U via the resistor R The resultant signal at point P is applied to the base of the transistor T through the resistor R and the capacitor C which are connected in series.

In the parabolic correction voltage generator G the emitter of the transistor T receives the voltage U through the resistor R and the collector of said transistor is directly connected to the source U The base of this transistor is controlled via the resistor R by a voltage prevailing at point P The capacitor C is connected between the base of the transistor T and ground and together with the resistor R it forms an integrating network.

The transistor T is connected like an emitter follower. The emitter is directly connected to the base of the transistor T the collector of which is connected to point P of the charging stage E The emitter of the transistor T is connected to ground through the series combination of resistors R and R The resistor R is decoupled by the capacitor C In the power amplifier EP the first three transistors T T and T are connected like emiter followers. The collector of the transistor T receives a voltage U and its emitter receives the voltage U through .a resistor R The base of the transistor T receives a voltage prevailing at point P The collectors of the transistors T and T receive the voltage U from the source S and the emitters receive the voltage U through the resistors R and R respectively; the emitter of the transistor T is connected to the base of the transistor T whose emitter is connected to the parallel-connected base electrodes of the transistors T and T The collectors of the transistors T and T are fed in parallel connection by the voltage U through the choke B The emitters of the transistors T and T are connected to ground through the resistors R and R respectively. The two parallelconnected deflection coils H and H are connected between ground and the collectors of the transistors T and T through the capacitor C and are shunted by the resistor R The elements used in a practical embodiment of the arrangement shown in FIG. 13 may have the following values: 

